US1583398A - Combustion regulation - Google Patents

Description

May 4 1926. 1,583,398

G. l-i. GIBSON COMBUSTION REGULATION Filed August 21, 1924 3 Sheets-Sheet 1 b w' INVENTOR,

607 f fog 14w Mt /AM ATTORNEY May 4, 1926.

G, H. GIBSON COMBUSTION REGULATION Filed August 21, 1924 3 Sheets-Sheet 2' INVENTOR ATTORNEY May 4 1926. 1,583,398

. G. H- GIBSON COMBUSTION REGULATION- Filed August 21 1924 3 Sheets-Sheet 5 INVENTOR W 2:. AW

ATTORNEY I Patented May 4,1926.

UNITED STATES GEORGEH. GIB SON, F MOHTCLAIR, NEW JERSEY.

'eomnns'rron REGULATION.

Application filed August 21, 1924. Serial No 733,289. I

' To all whom it may concern:

Be it known that I, GEORGE H. GIBSON,

a citizen of the United States, and resident. of Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Combustion Regulation, of which the following is a specification. v The general object of my present invention is to provide simple and effective provisions for varying the rate at which fuel is supplied to a boiler furnace in automatic response to the character of the gaseous products of combustion formed, so as to insure and maintain efficient combustion conditions.

My present invention is adapted for use in automatic combustion regulating sys-.

tems having provisions for varying the speed of the fuel feeding mechanism, and for varying the supply of air for combustion in automatic response to the boiler load, and was primarily devised to overcome the practical difliculty which has been experienced in the'operation of such systems in securing the proper rate of fuel feed at all times and under all conditions. In practice the rate of fuel feed is not'always strictlyproportional to the speed of the fuel feeding mechanism whether that mechanism is an ordinary mechanical stoker supplying solid fuel to a grate or is the fuel feeding mechanism of a powdered coal burning furnace. In the case of a furnace in which solid fuel is burned on a grate, failure to make the rate of fuel supply proportional to the rate of combustion results in an increase or decrease in the thickness, of the fuel bed with a consequent tendency to increase and decrease the CO content in the heating gases leaving the furnace. Even though the rate of fuel supply in such a furnace varies with the rate of combustion so that the desired average fuel bed thickness is maintained, clinker formations and holes in the fuel bed require the rate of fuel supplied to be varied from time to time to correspondingly thicken or thin the fuel bed in order to maintain a desirable CO, content in the heating gases.

Ina preferred practical mode of utilizing the invention in connection with a combustion regulating system in which the stoker speed and the rate at which air for combustion is supplied are automatically Russuu varied in accordance with the boiler load, I add to the regulating system means such as'an ordmary CO machine for modifying the stoker speed as the CO content in the flue gases decreases below. or rises above a predetern'nned desirable value. In a modified arrangement especially adapted for use with powdered coal burning furnaces, I regulate the speed of the blower supplying the carrier air for moving the powdered I coal into the combustion chamber in general response to the boiler load, but with a modifying action dependent upon the CO content in the flue gases,

In accordance with the present invention, the general rate of combustion may be va ried in inverse proportion to the steam 'pres sure or in direct proportion with the rate of steam generation, or in joint response to these two factors, but in an especially desirable arrangement, the rate at which air to support combustion is supplied is made dependent on the boiler steam pressure, whereas the rate at which fuel issupplied is made primarily responsive to the rate at which steam is generated, and is modified in accordance with the CO content in the flue gases.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a diagrammatic elevation of a boiler furnace burning solid coal provided with a stoker;

Fig. 2 is a diagrammatic sectional elevation of a powdered coal burning furnace; and

Fig. 3 is a view generally similar to Fig. 1 illustrating amodification of the apparatus shown in Fig. 1.

In the embodimentof my invention diagrammatically illustrated in Fig. 1, A represents the combustion chamber of a boiler.

damper D plied to the furnace through an inlet A opening at the under side of the grate and supplied with air under suitable pressure by a blower C operated by a motor C. A represents a discharge passage for ashes. A is the smoke stack connection, and D a draft regulating damper therein. The is adjusted by means of a motor D;

In accordance with the present invention, the combustion is controlled and regulated in response to the pressure of the steam and the composition of the flue gases in the manner now to be described. E represents a steam pressure gauge comprising a diaphragm E subjected to the boiler steam pressure as by means of a branch E from the boiler steam pipe A The thrust of the steam pressure against the diaphragm is opposed by the action of a lever E which bears against the upper side of the diaphragm E, and is fulcrumed at E and is connected to a loading device shown as a tension spring E, the tension of which may be adjusted by means of a nut E The free end of the lever E is connected to the operating lever F of a rheostat F and sweeps over a series of contacts F connected to sections of a resistance F scribed arrangement, as the steam pressure rises and falls, the rheostat lever F is moved to increase anddecrease, respectively, the amount of resistance in, and thereby to decrease or increase, respectively, the current strength in an electric control circuit.

This electric control circuit, as shown, comprises a supply conductor 1 connected to the lever F, the particular contact F 2 engaged by the lever F, the corresponding portion of the resistance F stant, and 011 the resistance in the circuit,

which in any given condition of operation is constant, and is automatically controlled as previously described by the steam pres'- sure through thevgauge E. A manually adjustable resistance R permits of change in the ratio between steanr pressure and the rate of combustion maintained by the regulating system.

In the control system illustrated in Fig; 1 the rate of combustion is primarily de- VVith the de-,.

the conductor 3 connecting the resistance F to one energizing the second energizing terminal pendent on the adjustment of the stack damper D which is automatically adjusted by the regulator GD to increase and decrease the flow of heating gases through the boiler furnace as theelectriccontrolcurrent increases and decreases in response to decreases and increases in the boiler steam pressure. The regulator GB tends to make increases and diminishes, the regulator-- GC operates to increase, and decrease the minus pressure or degree of vacuum in the furnace chamber as the rate of combustion increases and diminishes. The regulators GB, GC, and GD are all alike in principle in that each comprises means for balancing an electromagnetic force which is a functionof the strength of the control current against some other force which is, or is a function of, the condition to be regulated by tl-ie'particular regulator.

In the simple diagrammatically illustrated form of the regulator G0, the latter comprises a bell G which dips into sealing liquid within the container G and is subjected at its upper side to the pressure of the atmosphere and at its inner or under side to the pressure in the combustion chamber immediately above the grate transmitted to the interior of the hell by. the conduit G The bell G is suspended from one end'of a lever G fulcrumed at G" and the downward pull of the bell G, due to the excess of the pressure of the atmosphere over the pressure in the'furnace, is normally balanced by the action of an adjustable counterweight carried by the lever G coupled with an electromagnetic pull which is'a function of the electric control current and is produced by an electro n'iagnet comprising an armature G carried by the lever G, and the winding G, in the electric control circuit. On an in crease in the strength of the control current relative to the pressure differential acting on the bell G whether such increase be due to an adjustment of the rheostat F in response to variations in steam pressure, or to a change in fuel bed resistance to gas flow therethrough, or results from both of these causes, the lever G tilts to engage a contact 21. On a decrease inthe strength ofthe control current relative to the pressure differential the lever G tilts in the opposite direction and engages a contact 11. Ini'a neutral intermediate position of the lever G the latter does not engage either of the contacts 11 or 21.

When the lever G is tilted to engage either of the contacts 11 or 21 it energizes a reversible control motor C operating a rheostat C to thereby increase or decrease the speed of the blower motor C as required to restore the lever G to its neutral position. The rheostat C serves to increase or decrease the energizing current supplied to the motor C from supply conductors 10 and 20. The supply conductors 10 and associated with the device GC, as well as the conductors 10 and 20 associated with other regulating devices illustrated, can be connected to any suitable source,-for example, they may be A branches of the supply conductors 1 and 2.

The motor 0", as shown, has one'terminal connected to the supply conductor 20, a second terminal connected to the contact 11,

and a third terminal connected to the; conas diagrammatically tact 21. The lever G illustrated, is connected to the supply conductor 10 through the branch conductor 12. \Vhen the lever G engages the contact 21 one circuit including supply conductors 10 and 20, and branch conductors 12 and 22,

' and the conductor 14 of the reversible motor \Vhen,

, boiler, or,

. for the heating cuits for the reversiblemotor D 6 is energized, and the motor rotates in the direction required to so adjust the rheostat C as to decrease the speed of the blower C.

on theother hand, the lever G engages the contact 11 it thereby energizes the second circuit of the motor C which then rotates in the direction required to adjust the rheostat C to increase the speed of the blower C.

'The balance GD serves to open and close the. stack damper D as required to maintain a constant ratio between an electromagnetic force which is a function of the strength of the control current and the pressuredrop 'or draft loss in some portion of the furnace system in which the draft loss is approximately proportional to the weight rate of flow of the heating gases through the more accurately, to the square of that rate. As shown, the balance GD responds to the differential between the pressure at the inlet to the second, and the pressure at the outlet from the third of the passes gases across the water tubes, the pressures at these two points being transmitted to the balance GD by the pipes G and G \Vhen the pressure differential impressed on the balance GD through pipes G and G increases or decreases relative to the strength of the control current, the balance GD closes one or another of the control cirso that the latter is energized from the supply conductors 10 and 20 to close or open the damper D as required to restore the balance GD to its normal neutral condition the control current flowing through the electromagnetic winding of the balance GB and the outlet pressure of a small blower B, that pressure being a definite function of the blower speed and hence of the rate of fuel supply, since the blower B is driven by the stoker motor B As the strength of the control current energizing the winding of the balance. GB increases or decreases rela tive to the delivery pressure of the blower B, a reversible motor B is set into operation in the one direction or the other to adjust a rheostat B as required to thereby increase or decrease the speed of the Stoker motor necessary to restore the balance GB to its normal neutral position.

I have not thought it necessary illustrate the details of construction whichmay be employed in the balances GB and. .GD, because, as balances are similar in principle to the balance GC, and these balances comprise nothing novel with me.

On the contrary, these balances disclosed in my priorpatents' and applications, and in particular may be exactly similar in form to balances iilustrated in my application Serial No. 121,547, filed September 22, 1915.

In accordance w th the present invention, I employ a C0 machine H, which may be .the well known. Uhling instrument or other known form of instrument for creating a pressure in the pipe H of the instrument which varies n inverse proportion to the amount of CO inthe flue gas sample withdrawn from the last pass of the boiler through the conduit H 'In the diagrammatic representation of my invention illustrated the pressureun the pipe H is transmitted to the metallic U-tube I to thereby raise and lower a metal float J which floats on the'mercury or other conducting sealing As the' float J rises and contact carried by With the construction described, an increase in the steam pressure which corresponds in general to a decrease in the boiler load, brings about a throttling movement of the damper 1),, and a decrease in the rate of operation of the motors B and G" and there-, by in the rate at which fueland air for its herein to liquid, the wall of the 'already explained, these balances may be of thesame construction as branch 30 from the supply concombustion are supplied to the furnace. A

decrease in the steam pressure tends to produce an opening movement of the damper D the and an increase in the rate at which the motors Hand C supply fuel and air for its combustion to the furnace.

In accordance with the present invention, the rate at which fuel is supplied to the furnace is further niodih'ed by the action of' the .00, machine H which tends to increase the stoker speed and thereby thicken the fuel bed on a decrease in the amount of CO in the heating gases which'results from a thinning of the fuel bed and consequent increase in the amount of excess air, and convcrsely on a decrease in the amount. of CO from in the furnace a deficiency of excess air, the stoker is slowed down to allow the fuel bed to thin whereby the amount of excess air is increased and amore efiicient combustion is obtained. The CO machine H thus acts as an auxiliary controller to modify the stoker feed as required to compensate for variations between the actual rate of fuel feed and therate of combustion and thereby maintain a fuel bed of average thickness. In

' addition the CO machine H operates to thicken or thin the fuel bed when because of holes, clinker formations or from other cause the fuel bed, while of normal thickness, passes too much or too little excess air for the maintenance of the proper CO content in the stack gases.

In Fig; 2 I have illustrated the use of my invention in connection with powderedcoal burning boiler furnace to the combustion chan'iber AA of which powdered coal is su plied by a feeding mechanism B and a blower B supplying carrier air, the feeder I3 and blower B being both driven from a motor 13". Goal issupplied to the feeding mechanism through the chute B and the mixture of powdered coal and carrier air is passed into the combustion chamber zthrough one or more, and usually more, de-

. to the combustion chamber pressure trans control current increases I p v F g. 2 also an electric CO; machine HA 1s vidual burner nozzle B amount of secondary air livery pipes B each connected to an indi In Fig. 2 the regulator GO of Fig. v1, is jointly responsive mitted into the regulator through the pipe and to the electric control current. The regulator GC is employed'to adjust a claim per mechanism K througha reversible motor 0 and thereby increases 'or, decreases the supplied to the throi'lgh the ports the strength of the or diminishes. In

combustion chamber AA A in the furnace Wall, as

employed to control a reversible motor H v to adjust a contact H and thereby increase or diminish the portion .ofjthe resistance J".in shunt to-theregulator GB as the CO content in the stack gases diminishes below or increasesabove a predetermined value.

Aside from the features mentioned, the general arrangement and operatlon of the apgases such as would r-csult.

paratus shown in Fig. Eris identical with that of Fig. 1.

In the operation of a powdered fuel burning furnace there are no fuel bed holes and clinker formations to' give trouble as in grate fired furnaces but the rate at which the powdered fuel is fed varies very markedly with variations in certain characteristics of the fuel and partly with variations in its moisture content, so that with a given speed of the motor B there may be wide'variationsiin the rate at which fuel is actually passed into "the combustion chamber. This is COIHPCILSzIiQCl for by the operation of the CO, machine HA. Itis to be noted that the C0 machineIIA may be of one or another of various known forms of electrical CO, machines, and hence does not require speciiic explanation. It is also to be understood moreover, that in the apparatus of Fig. 2 the type of CO machine shown in Fig. 1 might be employed, and that the electrical CO machine of Fig. 2 might be employed in the apparatus of Fig. 1.

In the form of my invention illustrated in 3, the control provisions for adjust ing the stack damper I) and the speed of the bloweuG are identical with those illustrated'in Fig. 1. Furthermore, the stoker mechanism and the controlling provisions therefor including the CO machine H and the resistance shunt about the stoker regulator GB thereby controlled are shown of the same form as in Fig. 1. The control current to which the stoker speed regulator GB is subject in the arrangement of Fig. 3,

'Which is proportional to the square root of the difference between the static pressure and the total pressure in the steam pipe The static pressure is transmitted to the balance L by a pipe L ,and the total pressure is transmitted to the balanoe by the It isnot necessary to illustrate or describe the construction of the regulator in detail aselectric flow balances suitable "for the purpose are fully disclosed in my prior patents and applications, including my above mentioned application, Serial No. 121,547.

In the operation of the apparatus shown 1n Fig, 3 the rate of combustion, which depends primarily on the rate of air feed, is gov-- from the boiler. This is desirable in stoker fired furnaces because on an increase in the demand for steam, the stokors immediately begin to thicken the fuel bed, Whereas the supply of air does not begin to increase untillater when the increased rate of steam withdrawal results in a reduction in the pressure of the steam. In consequence, the

' of my invention now known to me, it will be apparent to those skilled in the art that formal departures may be made in the apparatus and methods specifically illustrated and described without departing from the spirit of my invention as set forth in the appended claims and that certain features of my invention may sometimes be used with advantage without a corresponding use of other features.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a combustion regulating system for a boiler furnace comprising provisions tending to vary the supply of fuel and air for its combustion in accordance with the boiler load, the improvement which consists in means .responsive to the CO content in the products of combustion for varying the ratio of fuel supply to air supply to minimize variations in said content.

2. In a combustion regulating system for a boiler furnace, the combination with'automatic fuel supply control provisions tending to make the rate of fuel supply propor- .tional to the boiler load, of means automatically responsive to the CO content in the products of combustion for increasing and decreasing the rate of fuel supply as said content decreases below and rises above a predetermined value.

3. In a combustion regulating system for a boiler furnace, the combination of means for creating an electric control current which is a function of the boiler load, a fuel feed regulator energized by said current and a C0 machine modifying the'action of 'the' control current on the regulator in'response to variations in the CO content of the products of combustion formed in the furnace. 4. .In a combustion regulating system for a boiler furnace, the combination with means for varying the rate of supply of air for combustion in inverse response to variations in the boiler steam pressure, of means tending to make the rate of fuel supply proportional to the rate at which steam is withdrawn from the boiler,

5. In a combustion regulating system for a boiler furnace, the combination with means for varying the rate of supply of air for combustion in inverseresponse to variations in the boiler steam pressure, of means tending to make the rate of fuel supply proportional to the rate at which steam is withdrawn fro the boiler, and means responsive to the CO content in the products of combustion formed for modifying the rate of fuel supply in inverse response to variations in said content from a predetermined value.

6. In a combustion regulating system for a boiler furnace comprising provisions tending to vary the supply of fuel andair for its combustion in accordance with the boiler load, the improvement which "consists in means responsive to the composition of the H products of combustion for varying the ratio of fuel supply to air supply to minimize variations in said composition.

7. Ina combustion regulating system for a boiler furnace, the combination with automatic fuel supply control provisions tending to make the rate of fuel supply proportional to the boiler load, of means automatically responsive to the composition of the productsof combustion for increasing and decreasing the rate of fuel supply as said icomposition varies in one way or another from a predetermined composition.

8. In a combustion regulating system for a boiler furnace, the combination with-means for varying the rate of supply of air for combustion in inverse response to variations in the boiler steam. pressure, of means tend ing to make the rate of fuel supply proportional to the rate at which steam is withdrawn from the boiler, and means responsive to the amount of a particular constituent in thevproducts of combustion formed, for modifying the rate of fuel supply in response to variations in said amount from a predetermined value.

Signed at Upper Montclair in the county of Essex and State of New Jerseythis 16th day of August, A, 1924,

' GEORGEH. GIBSON.

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